For both medical and industrial applications the use of polypeptides, including enzymes, are well-known in the art. As polypeptides may potentially cause an undesired immune response--dependent on the way of challenge--typically an IgG and/or IgE response, techniques for reducing it have been developed during the last three decades.
One technique is the "PEGylation" technique where a number of polymeric molecules are coupled to the polypeptide in question. When using this technique the immune system has difficulties in recognizing the epitopes on the polypeptide's surface responsible for the formation of antibodies, thereby reducing the immune response.
For polypeptides introduced directly into the circulatory system of the human body to give a particular physiological effect (i.e. pharmaceuticals) the typical potential immune response is an IgG and/or IgM response, while polypeptides which are inhaled through the respiratory system (i.e. industrial polypeptide) potentially may cause an IgE response (i.e. allergic response).
One of the theories explaining the reduced immune response is that the polymeric molecule(s) shield(s) epitope(s) on the surface of the polypeptide responsible for the immune response leading to antibody formation. Another theory or at least a partial factor is that the heavier the conjugate is, the more reduced immune response is obtained.
U.S. Pat. No. 4,179,337 concerns non-immunogenic polypeptides, such as enzymes and peptide hormones coupled to polyethylene glycol (PEG) or polypropylene glycol (PPG). At least 15% of the polypeptides' physiological activity are maintained. The use of PEG's with a molecular weight in the range from 750 Da to 6,000 Da are exemplified in the patent. The polypeptides are not used for industrial applications.
WO 96/17929 (Novo Nordisk A/S) concerns modified polypeptide conjugates coupled to polymeric molecules such as PEG. The modified enzymes may be used for a number of industrial applications. The molecular weight of the polymeric molecules coupled to the polypeptides in the Examples are 5,000, 15,000 and 35,000 Da, respectively.